Squid liquid embolic agent deemed safe and effective for high-grade DAVFs

Markus Möhlenbruch

The Squid liquid embolic agent (Balt) has been deemed safe and effective in treating high-grade dural arteriovenous fistulas (DAVFs), and serves to expand the armamentarium for neurointerventionists treating DAVFs and other intracranial vascular malformations.

Markus Möhlenbruch (Heidelberg University Hospital, Heidelberg, Germany) and colleagues recently published the results from a prospective, observational multicentre study of this endovascular embolisation treatment in the Journal of NeuroInterventional Surgery.

“Squid is a promising liquid embolic agent for the embolisation of high-grade DAVFs,” they write. “In this prospective, multicentre study, embolisation using Squid was associated with an acceptable complication rate and a high occlusion rate.”

The study’s authors begin their report by noting that endovascular embolisation became established as a feasible treatment option for cranial DAVFs—primarily following the introduction of the Onyx liquid embolic agent (ev3/Medtronic) in the mid-2000s—and that newer agents like the novel, non-adhesive, precipitating Squid have aimed to overcome existing shortcomings and further improve the success of DAVF embolisation.

“The two major innovations of the new liquid embolic, Squid, in comparison with Onyx, are the size of the tantalum grains, which are admixed to the agent, and the availability of the low-viscosity version, Squid 12,” they write, but note that all other components of the two agents are identical.

As such, Möhlenbruch and colleagues set out to assess the safety, efficacy and short-term outcomes of DAVF treatment with this liquid embolic via the prospective, observational LIQUID study, which was conducted across eight German neurovascular centres. The primary outcome measures were safety—defined as morbidity and mortality—and the occlusion rate 90–180 days after treatment.

A total of 53 patients (mean age=59.8 years, 22.6% female) with high-grade (Cognard type ≥3) DAVFs were treated with the Squid liquid embolic agent across 55 treatment sessions. Of the included DAVFs, 56.6% were Cognard type III, 41.5% were type IV, and 18.9% were ruptured, the authors report. The Squid 18 was used in 83.6% of treatments while the Squid 12 was deployed in 32.7%.

Outlining results from the LIQUID study, Möhlenbruch and colleagues state that the overall rate of intraprocedural or postprocedural adverse events was 18.2%, and procedure-related adverse events resulting in permanent morbidity were observed in 3.6% of cases. One patient (1.8%) died unrelated to the procedure due to pulmonary embolism.

In addition, the immediate complete occlusion rate using Squid only was 92.5%. In one patient, after partial embolisation with Squid, transvenous coiling was performed to achieve complete occlusion, resulting in an overall, immediate complete occlusion rate of 94.3%. The final complete occlusion rate at 90–180 days was 93.2%, the authors add, noting that this core laboratory-rated rate of occlusion is “slightly higher than previously published occlusion rates on endovascular embolisation of DAVFs”.

Regarding functional outcomes, Möhlenbruch and colleagues report that—after a mean follow-up of 5.5 months—the modified Rankin Scale (mRS) score was stable or improved 93% of the time. However, a worsening mRS score was deemed to have been related to the procedure in one patient (1.8%).

“Squid, which features several modifications compared with the established agent, Onyx, expands the armamentarium of liquid embolic agents for the treatment of DAVFs,” they continue.

Despite this, the authors also point out that, even with these potential advantages in mind, impedance of a plug formation; early distal embolisation; and a potentially higher ability to diffuse into collateral meningeal arteries, constitute three major drawbacks associated with embolisation utilising low-viscosity agents. And, while none were directly observed in the LIQUID study, these drawbacks should be known and considered by interventionists using Squid 12.

Möhlenbruch and colleagues go on to briefly acknowledge their study’s limitations, including a relatively low number of patients, the fact that 9.3% of patients did not have data available for follow-up, and the lack of a control group involving other embolic agents. As such, while they claim that this is the largest study reporting on DAVF embolisation using Squid to date—and the first ever prospective study on the endovascular treatment of high-grade DAVFs in “the era of liquid embolic agents”—the scope for comparisons between Squid and other agents is limited.


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